Document U.S. Pat. No. 1,684,944 discloses a memory slide for a vehicle seat that comprises:
a "fixed" first rail deigned to be secured to the vehicle;
a "moving" second rail designed to support the seat proper, said moving rail being disposed parallel to the fixed rail and being mounted to slide along said fixed rail;
first locking means for locking the moving rail relative to the fixed rail, said first locking means being capable of being placed either in a locked state in which the moving rail is locked relative to the fixed rail, or else in an unlocked state in which the moving rail is free to slide along the fixed rail;
a memory shoe displaceable in translation along the fixed rail and limiting movement of the moving rail in the longitudinal direction of the fixed rail, thereby defining a memorized position of the moving rail, the memory shoe including a length of rail having the same section as the moving rail, which length is slidably mounted to slide along the fixed rail in the same manner as said moving rail;
second locking means for locking the memory shoe relative to the fixed rail, said second locking means being capable of being placed either in a locked state in which the memory shoe is locked relative to the fixed rail, or else in an unlocked state in which the memory shoe is free to slide along the fixed rail;
coupling means for coupling the moving rail to the memory shoe, said coupling means being in a coupled state at least when the first and second locking means are both in the unlocked state, the moving rail and the memory shoe then being secured to each other, and said coupling means being in an uncoupled state at least when the first locking means are in the unlocked state while the second locking means are in the locked state, the moving rail and the memory shoe then being no longer secured to each other;
first control means for placing the first and second locking means simultaneously in the unlocked state; and
second control means for placing the first locking means only in the unlocked state, the second locking means then remaining in the locked state.
The seat disclosed in the above-mentioned document does not include a safety belt.
However, vehicle seats are known from elsewhere that do include safety belts in which at least one of the three fixing points of the belt is connected to the seat.
As a general rule, this fixing point is connected to the structure of the seat proper, such that when the vehicle is subjected to a shock giving rise to a large force on the belt fixing points, in particular in the event of an accident, this force may possibly give rise to the fixed rail and the moving rail that support the seat being deformed.
There is then a risk that the seat will no longer be capable of sliding forwards and this can have very severe consequences if the seat in question is a front seat of a two-door vehicle: under such circumstances, firstly the back seat passengers run the risk of being greatly impeded in any attempt to get out of the vehicle quickly after an accident, and secondly, emergency services can likewise be impeded in gaining access to the back seats if the back seat passengers are injured.